package pack;

import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner  sc = new Scanner(System.in);
		while (sc.hasNext()) {
			int n = sc.nextInt();
			if(n <= 1) {
				System.out.println("no");
				continue;
			}
			int i = 2;
			for(; i * i <= n; i++)
				if(n % i == 0) {
					System.out.println("no");
					break;
				}
			if(i * i > n)
				System.out.println("yes");
		}
		sc.close();
	}

}
